Sat, March 12, 2016 Turnagain Pass Avalanche Forecast

Sat, March 12th, 2016

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

3 - Considerable

Below Treeline

Below 1,000'

0 - No Rating

1 - Low

2 - Moderate

3 - Considerable

4 - High

5 - Extreme


Travel Advice	Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.	Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.	Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential.	Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.	Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches	Natural and human-triggered avalanches unlikely.	Natural avalanches unlikely; human-triggered avalanches possible.	Natural avalanches possible; human-triggered avalanches likely.	Natural avalanches likely; human-triggered avalanches very likely.	Natural and human-triggered avalanches certain.
Avalanche Size and Distribution	Small avalanches in isolated areas or extreme terrain.	Small avalanches in specific areas; or large avalanches in isolated areas.	Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.	Large avalanches in many areas; or very large avalanches in specific areas.	Very large avalanches in many areas.

Avalanche Problem 1

Storm Slabs

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

More info at Avalanche.org

A quick hitting storm rolled through the region yesterday bringing a much needed ‘re-fresh’ to Turnagain Pass. The Turnagain Pass SNOTEL station reported 9″ of new snow beginning yesterday around noon and ending last night around midnight. This usually equates to around a foot in the Alpine. The rain/snow line was hovering just under the parking lot elevations on the Pass, around 1,000′. We did get a report of a natural avalanche seen across the Arm from Girdwood, see that and additonal info HERE. This new snow is great news, but a new set of avalanche conditions will come with it as well. These are:

Wind Slabs: Winds associated with the snowfall were moderate to strong from a generally Easterly direction. This is a perfect recipe for forming wind slabs above treeline that could be anywhere from 1-2+’ thick. How well these fresh slabs are bonding with the old snow surface is uncertain – and something to be wary of today. The old snow surface was quite variable, harboring sun crusts on Southerly aspects, wind crusts and loose faceting snow. All of these surfaces are not likely to promote good bonding right away and our hackles should be up. Things to watch for today:

1- Recent avalanches, the skies should clear for good visibility
2- Cracking or collapsing in the new snow
3- Slopes that have been windloaded – Avoid these today, give them a chance to adjust
4- SUN…. If the sun comes out slabs could release naturally with the warming!

Loose Snow Avalanches: Once the sun does come out (today or tomorrow) damp/wet sluffs are likely to run naturally. These will also be easily triggered by a person. Sluffs should entrain mostly just the new snow, so how much new snow is on a slope will depend on how large the sluff is.

Cornices: Another round of snow and wind will only add to the weight of these truck size features overhanging many slopes. Extra caution is warranted when choosing how you travel along ridgelines – give cornices an extra wide berth. Also, limit time under these, they could fall on their own and the sun warming them will add to this possibility.

Avalanche Problem 2

Glide Avalanches

Glide Avalanches

Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.

More info at Avalanche.org

AVOID travel under glide cracks. This week has been a particularly active glide avalanche cycle. Glide cracks continue to threaten large areas of terrain throughout Turnagain Pass, Girdwood, and Summit Lake. There were several new glide avalanches seen Wednesday from the Seward Hwy, and a large glide released on the East face of Seattle Ridge a few days ago. Glide cracks are on all aspects within the mid-elevation band (1000′-2500′), and some areas like the SW face of Cornbiscuit and Tincan are covered. This avalanche problem is impossible to predict and is not associated with human triggers. We have been talking about the glide avalanche problem for over two months in the advisory and as long as glide cracks continue to open up, move and release, we will stress the importance of avoiding them.

Weather

Sat, March 12th, 2016

Yesterday saw a quick moving disturbance move through. Visibility was poor as rain fell below 800-1,000′ with snow above. The Turnagain Pass SNOTEL site has reported 9″ of new snow at 2,000′. Winds associated with the snowfall were 20-25mph from the East along the ridgetops with stronger gusts. Temperatures have been warm, in the mid 30’s F at 1,000′ and the mid 20’sF at 3,500′.

Overnight, snowfall has stopped and winds have died down. For today, skies should begin to clear up as the system exists the region; we are expecting the sun to come out for the afternoon. Winds today are expected to be light, 5-10mph, from a generally East direction and temperatures warm, up to 40F at 1,000′ and the upper 20’sF in the Alpine.

Sunday and into Monday looks to be mostly clear as well with sunny skies and light Easterly ridgetop winds.

PRECIPITATION 24-hour data (6am – 6am)

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	31	9	0.9	143
Summit Lake (1400′)	35	0	0	43
Alyeska Mid (1700′)	32	5	0.7	110

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	24	NE	18	43
Seattle Ridge (2400′)	26	SE	16	35

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
05/13/24	Turnagain	Observation: Eddie’s, Sunburst, Seattle, Cornbiscuit, Pete’s South	H Thamm
05/13/24	Turnagain	Observation: Turnagain Pass non-motorized side	Amy Holman
05/12/24	Turnagain	Observation: Warm up Bowl	Tony Naciuk
05/07/24	Turnagain	Observation: Turnagain Pass Wet Slabs	A S
04/29/24	Turnagain	Avalanche: Turnagain aerial obs	Tully Hamer
04/27/24	Turnagain	Observation: Johnson Pass	Noah Mery
04/23/24	Turnagain	Observation: Turnagain Sunny Side	Travis SMITH
04/21/24	Turnagain	Observation: Bertha Creek	Anonymous
04/20/24	Turnagain	Avalanche: Spokane Creek	Schauer/ Mailly Forecaster
04/16/24	Turnagain	Observation: Cornbiscuit	Krueger / Matthys Forecaster

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